川西新场地区须二段气藏气水分布规律

Complex gas water distribution law of the gas reservoir of the second member of Xujiahe Formation in Xinchang area, western Sichuan

四川盆地川西坳陷新场构造带须家河组二段(须二段)气藏气水关系复杂,已成为制约气藏高效开发的主要因素之一。通过分析该气藏气水分布特征,从构造、盖隔层分布、储层特征和油气运聚模式等方面,对气藏的复杂气水关系主控因素进行了研究。结果表明:新场须二段致密气藏气水分布横向上主要受储层强非均质性影响,储渗体间连通性差,局部构造高点和断缝体是油气聚集有利部位;纵向上被区域盖层和连续分布的隔层分隔为须二上亚段和须二中亚段2套相对独立的气水系统;受储层低孔低渗及孔隙结构差影响,每套气水系统都有较厚的(25~170 m)气水过渡带;储层强非均质性、盖隔层和断裂等多方面的影响导致2种气水分布模式,其中:断缝输导模式在须二上亚段具有较厚的气顶,底水主要分布于须二中亚段底部;源储接触模式在每套气水系统中均呈现为薄气顶、厚气水过渡带、底水的分布特征。气水分布模式的建立为该气藏的避水开发提供了依据,并指出构造相对高部位、近烃源断层、区域盖层及隔层下的气顶是开发的首选目标。

The gas water relationship in the second member of the Xujiahe Formation(Xu 2 Member)in the Xinchang structural belt of the Western Sichuan Depression is extremely complex,and has become one of the main factors restricting the efficient development of gas reservoirs.By analyzing the distribution characteristics of gas and water in the gas reservoir,the main controlling factors of the complex gas water relationship in the gas reservoir were studied from aspects such as structure,distribution of cap and barrier layers,reservoir charac⁃teristics,and oil and gas migration and accumulation patterns.The results show that horizontally,the tight gas reservoir of Xu 2 Member in Xinchang area is mainly affected by the strong heterogeneity of the reservoir.The connectivity between the reservoir and permeability bodies is poor,and local structural highs and fault fracture bodies are favorable locations for oil and gas accumulation.Vertically separated by regional caprocks and contin⁃uously distributed compartments,it is divided into two relatively independent gas-water systems:the upper and middle sub sections of Xu 2 Member.Due to the low porosity and permeability of the reservoir and poor pore structure,each gas-water system has a thick(25-170 m)gas-water transition zone.The strong heterogeneity of reservoirs,caprocks,and fractures have led to two types of gas water distribution patterns.The fracture trans⁃port pattern has a thick gas cap in the upper sub section of Xu 2 Member,and the bottom water is mainly distrib⁃uted at the bottom of the middle sub section of Xu 2 Member.The source reservoir contact pattern presents the distribution characteristics of thin gas cap,thick gas water transition zone,and bottom water in each gas water system.The establishment of the gas water distribution model provides a basis for the water avoidance develop⁃ment of the gas reservoir,and points out that the preferred targets for development are relatively high structural areas,near hydrocarbon source faults,regional caprocks,and gas caps under the interlayer.